Performance Max is stealing credit from your Search campaigns. Here's how to take it back.

If you’ve launched Performance Max in the last twelve months and noticed your branded Search campaigns mysteriously losing volume, you are not imagining it.

This is the single most common — and most expensive — pattern we find when auditing UK Google Ads accounts. Performance Max is doing exactly what Google designed it to do, and Google is happy with the result. You probably aren’t, once you understand what’s actually happening.

This article walks through the pattern in plain English, shows you how to confirm it in your own data, and then gives you the exact playbook for excluding your brand from PMax — including the small but important fixes that most “PMax brand exclusion guides” leave out.

What Performance Max actually does, beyond the marketing

Performance Max is Google’s machine-learning campaign type that decides, on a query-by-query basis, where your ads appear: Search, Display, YouTube, Gmail, Discover, Maps. You give it a budget, some creative assets, an audience signal or two, and a goal. The algorithm does the rest.

The pitch is appealing. One campaign instead of six. No keyword research. The machine optimises across surfaces in real time. Conversion volume goes up.

The catch is in where that conversion volume comes from.

Performance Max is allowed to compete on every query Google can match to your assets — including queries you were already winning, for free, through your branded Search campaigns. When someone types “your company name” into Google, PMax can step in and intercept that click. The conversion logs against PMax. The branded Search campaign quietly loses a click it would have served at a fraction of the CPC. Your monthly report says PMax is your best campaign.

It is not. It is a campaign that learned to take credit.

The pattern, in three numbers

Here’s what cannibalisation looks like in real account data we’ve seen, anonymised and slightly rounded for readability.

A UK B2B services firm with a recognisable brand:

• Branded Search campaign, prior 12 months: ~12,000 clicks/month at £0.42 average CPC
• PMax launches in month 13. By month 16, branded Search clicks have dropped to ~7,500/month. PMax is now reporting ~5,000 conversions/month at a £6.80 CPA — quietly Google’s “best” campaign in the account.
• Total revenue: flat. Total spend: up by ~£3,200 a month, almost all of it on PMax.

The clicks didn’t disappear. PMax intercepted them. And because branded queries convert at much higher rates than cold prospecting, PMax’s reported CPA looked great — it was getting credit for prospects who were already a yes.

The fix, when this account excluded brand terms from PMax, was almost comical: PMax CPA went up (because it now had to earn cold conversions), branded Search clicks recovered, total revenue stayed flat, and total spend dropped by £2,800 a month. Same revenue, less spend. That’s a £33,600/year recovery without changing budget, creative or strategy.

This pattern is now common enough that the joke in our office is “audit, find the leak, run the brand exclusion, save four figures a month.” That joke would not survive contact with a balanced sample. But it survives contact with most of them.

How to confirm cannibalisation in your own account

Before you exclude anything, prove the pattern is happening. There are three checks, none of which take more than half an hour.

Check 1: branded Search impressions, before and after PMax

Open Campaigns in Google Ads, filter to your branded Search campaigns, and pull a 90-day window covering before-and-after PMax launched. Add the columns Impressions, Clicks, CTR, Cost.

If branded Search impressions dropped meaningfully when PMax went live — not just clicks, but impressions — that is a strong signal. Impressions falling means Google is no longer serving your branded Search ad on queries it used to. Almost always, that’s because PMax is winning the auction internally.

Check 2: search-term insights inside PMax

PMax used to be a black box. Google now exposes a Search themes and Insights → Search terms report inside each PMax campaign. Open it. Sort by spend.

If you see your own brand name, your founder’s name, your domain, or obvious branded variants (“Nerdster Design,” “Nerdster Design London,” “is Nerdster Design any good”) in the top spend rows, PMax is hoovering up branded queries.

You can also see this through Insights → Audience insights, where the “Search categories” or “Customers searched for” panel will often surface branded clusters.

Check 3: Google Analytics or your CRM

Look at the source/medium reports for the period before and after PMax launched. If google / cpc traffic is broadly flat, but the share within google / cpc shifts heavily towards PMax campaign IDs (typically named something like “Performance Max — All”), that’s the same finding from a different angle. Conversions weren’t created — they were rebadged.

If two of these three checks confirm the pattern, you have cannibalisation. Time to fix it.

The brand exclusion playbook, step by step

There are two routes to excluding brand from PMax, and the right one depends on how recent your account is. Most UK accounts now have access to the cleaner of the two.

Route A: account-level brand exclusions (the modern way)

Since 2024, Google Ads has allowed account-level brand exclusion lists that apply to every PMax and AI Max campaign automatically.

1. Navigate to Tools and settings → Shared library → Brand lists.
2. Click Create brand list. Add your primary brand and any obvious variants — common misspellings, the .com or .co.uk domain, your founder’s name if you trade on it, sister-company names if you don’t want PMax bidding on them.
3. Save the list.
4. Open each Performance Max campaign you want to apply it to. Go to Settings → Brand exclusions and add the brand list you just created.
5. Repeat for any AI Max for Search campaigns, which use the same exclusion mechanism.

Important: Google’s interface lets you add brands as either exclude or include only. You want exclude. Read the option labels twice — getting it backwards turns PMax into a brand-only campaign, which is the exact opposite of what you’re trying to do.

Route B: negative keyword lists at the account level (the older way)

If your account doesn’t have brand lists yet, or if you want belt-and-braces protection, you can add negative keywords at the account level that block branded queries from triggering PMax.

1. Tools and settings → Shared library → Negative keyword lists.
2. Create a list called something like “PMax brand block.” Add your brand variants as exact-match negatives, then as phrase-match negatives. Cover the common misspellings.
3. Apply the list to every Performance Max campaign. Apply it specifically to PMax — not to your branded Search campaigns, obviously, or you’ll have just turned off the Search campaign you’re trying to protect.

Account-level negative keywords for PMax is a 2023+ feature. If your interface doesn’t show it, you’re either on an older Ads account that hasn’t had the feature rolled out yet (rare in 2026) or you’re looking in the wrong place.

Route C: contact your Google rep (yes, really)

For accounts spending less than £50,000/month, this won’t apply to you. For larger accounts, your assigned Google rep can apply server-side brand exclusions that don’t appear in the UI. Email them. Be specific: “Please exclude these exact-match branded queries from our PMax campaigns at the account level.” It usually takes 24-48 hours and they’ll confirm by email.

We’ve seen this work for accounts where the UI exclusions weren’t being honoured fully — typically because PMax was matching on close variants the negative-keyword list didn’t anticipate.

What to expect after exclusion

If you’ve genuinely had cannibalisation, the pattern in the four weeks following exclusion is consistent enough to be predictable:

Week 1. PMax conversions drop sharply. PMax CPA rises, sometimes dramatically (we’ve seen £6 CPAs become £25 CPAs overnight). This is good news, not bad — the algorithm has lost its cheat code and is now showing you its true cold-prospecting performance.

Week 2. Branded Search clicks and conversions recover, usually to within 90% of their pre-PMax level. CTR on branded Search recovers fully.

Week 3-4. PMax stabilises at its honest CPA. You now know what you’re actually paying for cold conversions, and you can decide whether that CPA is acceptable or whether the budget belongs elsewhere — Search, demand-gen, organic, anywhere.

If PMax conversions don’t recover at all and stay near zero, that’s also useful information: PMax was not finding you cold prospects. It was a branded-traffic interceptor with extra steps. You can pause it without losing real revenue.

The mistakes we see, even from people who know about brand exclusion

Three pitfalls worth avoiding.

Excluding only the exact brand spelling. If your brand is “Nerdster Design,” you also need “nerdster design,” “Nerdster,” “nerdsterdesign,” “Nerdster Design London,” and the .com / .co.uk domain. PMax matches loosely. Cover the cluster, not just the canonical spelling.

Forgetting AI Max for Search. If you’re running AI Max — Google’s newer AI-driven campaign type — it uses the same brand-exclusion mechanism as PMax and needs the same treatment. Many teams exclude PMax and forget AI Max, which then quietly does the same job.

Not removing branded audience signals. Audience signals on PMax aren’t hard targeting, but they’re hints. If your “all customers” or “website visitors” audience signal is heavily branded (people who already know you), you’re still pointing PMax at warm traffic. Replace those signals with cold-prospecting custom segments — in-market audiences, lookalikes of your customer list, search-keyword custom segments around problem-aware queries.

Pausing PMax instead of fixing it. A natural reaction once you understand the pattern is to nuke PMax entirely. Sometimes that’s correct. But for many accounts, PMax with brand excluded and proper cold audience signals does genuinely produce incremental conversions — just at a higher CPA than the cooked numbers suggested. Don’t throw out the campaign type. Throw out the cannibalisation.

A note on Google’s incentives

It’s tempting to read all this as Google being malicious. It isn’t, exactly. PMax is doing the job it was given: maximise reported conversions inside your campaign, on the surfaces it has access to. Google’s incentive is for that number to be as high as possible, because high reported conversions sell more PMax campaigns. Your incentive is for incremental conversions to be as high as possible.

Those two goals look identical until you start measuring incrementality. They diverge sharply when you do.

This is why we audit before we ever take on a Google Ads management retainer. About a third of accounts we audit have this exact PMax cannibalisation pattern, and the fix takes a fortnight, not a year-long retainer. If that’s the only thing the audit finds, we’ll tell you, send you a written punch list, and walk away. About a third of audits end that way. That is fine.

If you want the same checks run on your account, we offer a free 30-minute Google Ads waste audit — written punch list, 48-hour turnaround, no obligation. Bring the account; we’ll bring the screen-share.